I really enjoyed your post; a very thoughtful look at the potential downsides of polyamory. So much of what I've read about it is written by poly practitioners/advocates. It's like trying to find out how good a make of car is by talking to the car salesman. As an old person, I think much of what you say is true of anyone with age, regardless of their relationship orientation. Our choices get limited in many ways, and people tend to hunker down into some configuration as they age and stay there until the end. We're less open to change, unfortunately, and opportunities dry up. I think age needs to be re-defined like relationships, and looked at outside the usual box our culture puts it in. You're alive until you die. Live that way